Causation of Everything
We’ve had causation come up a few times on the blog before (particularly in Mike’s discussion of miracles). For this post, I want to raise some questions about what to say when causation get really big—when we start talking about the state of everything at one moment in time causing everything at the next—and whether such talk is sensible. Such questions are particularly relevant in the context of cosmology.
Usually when we make causal claims or explanations, we’re talking about a local causation: a particular event (or event-type, or state of affairs) that occurs in a relative small finite region of space-time, causing an event at another. We might speak of the high-pitched tone causing the glass to break, or CO2 emissions causing increased polar ice melting. While we might have some difficulty in identifying very diverse and diffuse causes and effects, we presume that the causes and effects are still local.
But what about system-wide causal claims? Assuming that a set of billiard balls, for example, constitutes an effectively closed system, could we claim that the entire configuration of billiard balls at one time causes the entire configuration at the next moment in time? Or could we claim that the state of the entire universe at one time causes the state of the universe at a later time? (Note that I’ll be leaving ‘a moment in time’ as a loose and vague notion here—whatever account of causation we use will have to be compatible with general relativity, but I won’t go into how that might be done here.)
In ‘On the Notion of Cause’ (1912−3), Russell famously argued that we should jettison the notion of causation altogether. His main concern was that, given the global laws we have in fundamental physics, nothing less than the entire state of the system at a given time would be enough (given the laws) to necessitate any event in the next. So as far as we think causation requires nomic necessitation, we would need to consider the entire state of the system as a cause. And he took this to be a reductio of the position: if causes were also to be general types of events, of the type science could investigate, there could be no cause-based science. Here’s Russell:
In order to be sure of the expected effect, we must know that there is nothing in the environment to interfere with it. But this means that the supposed cause is not, by itself, adequate to insure the effect. And as soon as we include the environment, the probability of repetition is diminished, until at last, when the whole environment is included, the probability of repetition becomes almost nil. (Russell 1912−13, pp. 7−8)
Either the causes would be so extensive and detailed as to be unique, and not the subject of scientific investigation, or they would not necessitate their effects. Science has to study repeatable events, and system-wide states would never be repeatable in the way required.
So, in Russell’s work we actually have an argument in favour of system-wide causation: it allows us to take the causal relation to be necessitation by fundamental laws. But we also have an argument against system-wide causation: it isn’t about the kind of repeatable events that science is concerned with. The argument in favour of system-wide causation seems clear enough, but what are we to make of the argument against? It seems that cosmology is precisely a field that is interested in non-repeatable events. Perhaps cosmology does not describe events at a sufficiently fine-grained level to explain how many actual events are nomically necessitated, but what about large-scale phenomena? Surely cosmology aims to account for those?
However, some later developments that followed Russell’s work didn’t advocate for system-wide causation, but dropped the requirement that causes had to nomically necessitate their effects. Instead, we were to explain what was going in causation using counterfactuals and notions of intervention. Claiming a causes b is roughly to claim that had we intervened on a in a suitably surgical of way, this would have been a way of influencing b. The interventions themselves were characterised as causal processes, as processes that that disrupt some of the causal chains already present in the system, while leaving others intact, and so allows us to test what causal chains there are. The main expositors of this approach are Woodward (2003) and Pearl (2000). These interventionist approaches don’t attempt to reduce causation to something else, but instead offer an elucidation of various causal notions in terms of other ones.
However, under such the interventionist approach, it’s hard to see how we can talk about system-wide causation. Interventions were envisaged as process that originated from outside the system we were studying. How is this approach to work when there is nothing outside the system? Here is Pearl on the issue:
…scientists rarely consider the entirety of the universe as an object of investigation. In most cases the scientist carves a piece from the universe and proclaims that piece in – namely, the focus of investigation. The rest of the universe is then considered out or background and is summarized by what we call boundary conditions. This choice of ins and outs creates asymmetry in the way we look at things, and it is this asymmetry that permits us to talk about “outside intervention” and hence about causality and cause-effect directionality. (Pearl 2000, p. 350).
‘If you wish to include the entire universe in the model, causality disappears because interventions disappear – the manipulator and the manipulated loose their distinction. (Pearl 2000, p. 349−50).
We might claim this as a feature of the interventionist approach: the approach makes it clear how the causal structure of the world is tied to a particular limited perspective we take on it as experimenter or intervener, dividing the world up, and is not something that can be understood outside of these divisions. Are we then content to cease dealing with causal notions in sciences like cosmology?
There are a few remaining options on the table that I’ll note briefly. One is to start with the interventionist framework, but then extend our causal notions so that they can be system-wide. We might, for example, attempt to reduce the interventionist counterfactuals to law-based ones that can then be applied to whole systems—I take Albert (2000) and Lower (2007) to follow this route. Or we might keep causation as a primitive relation that holds between local events, and build up system-wide causes out of those. Another quite different option is to go pluralist about the notion of causation: perhaps we were wrong to think that a single notion applied to all contexts. We should keep nomic necessitation as what counts for cosmology, and intervention as what counts for other contexts.
Whatever option we take here, the case of cosmology seems a useful testing ground for accounts of causation and their commitments regarding global causes.
Albert, David Z. 2000. Time and Chance. Cambridge, Mass.: Harvard University Press.
Loewer, Barry. 2007. Counterfactuals and the Second Law. in Causation, Physics, and the Constitution of Reality, ed. Huw Price and Richard Corry, 293−326. Oxford: Oxford University Press.
Pearl, Judea. 2000. Causality. New York: Cambridge University Press.
Russell, Bertrand. 1912−13. On the Notion of Cause. Proceedings of the Aristotelian Society, New Series. 13: 1-26.
Woodward, James. 2003. Making Things Happen: A Theory of Causal Explanation. Oxford: Oxford University Press.